The role of the undecided voter has rarely, if ever, seemed so important.

And as the New Hampshire primary gets under way, those voters will have the power to make or break campaigns.

Among the most prized are the independents, who make up as many as four in 10 of total voters and can choose to vote in either the Democratic or Republican race. A majority of them are expected to opt for the former.

Desperate to woo them, the presidential candidates for both parties criss-crossed the state on the last full day of campaigning, racking up almost 50 events between them.

And the New Hampshire voters, aware of their important status as first in the US to hold their presidential primary election, turned out in their droves to hear them.

Jane and Joe Edmonds were among several dozen people to wait in a slush-covered square in Keene to hear John McCain, who is enjoying a late lead in the Republican polls.

"We're here because we are undecided," said Mr Edmonds, an airline pilot, 38. "I'm leaning towards McCain and Rudy Giuliani - I go back and forth a bit."

Standing near them, Marci Cooke, from Westmoreland, had been at a Barack Obama rally on Sunday night but wanted to see Senator McCain too before making up her mind.

"I'm always interested to hear what everyone has to say because I'm from New Hampshire," she said. "I'm probably going to vote for Obama but I'm not quite sure."

Show of emotion

Senator Obama, riding a wave of momentum from his win in the Iowa caucuses last week, has packed out school gyms and auditoriums in New Hampshire.

Emotion surfaced as Mrs Clinton campaigned

His supporters have planted many of the banners that dot the banks of snow beside the state's tree-lined roads and cluster at every road junction.

The latest polls gave him a several-point lead over rival Hillary Clinton, who slipped back after leading in the state for months.

She sought to fight back in the four days since her disappointment in Iowa with a feisty debate appearance at the weekend and a string of well-attended events of her own.

But the moment likely to dominate headlines from the final day of campaigning was a rare show of emotion from the former First Lady.

Asked by a woman at a breakfast meeting in a Portsmouth cafe how she kept going each day, Mrs Clinton's voice faltered and her eyes appeared to well up.

"I just don't want to see us fall backward as a nation," she replied. "I mean, this is very personal for me. Not just political. I see what's happening. We have to reverse it."

A few hours later, and it was time for laughter at a rally at Salem High School, where two young male hecklers were ejected after repeatedly shouting: "Iron my shirt!"

"Oh, the remnants of sexism, alive and well," responded Mrs Clinton, adding that it demonstrated her mission to break through "the highest and hardest glass ceiling".

Outsider

"Change" has become the word of the moment, with many of the candidates tweaking their campaign speeches to pick up on the mood from Iowa's caucuses.

But it remains unclear whose brand of change will prove the most popular.

Mr Obama, who if elected would become the first black American president, has campaigned on a platform of "change we can believe in" and extolled the power of hope.

This is a pretty historic time and this is when New Hampshire gets to shine

Chris Gagnon John Edwards supporter

Republican Mitt Romney, who came second in Iowa to former Arkansas Governor Mike Huckabee, has presented himself in New Hampshire as someone who can bring change as a Washington outsider.

Meanwhile, Mrs Clinton has spoken of offering change with experience.

John Edwards, who pipped her to second place in Iowa, embarked on his second 36-hour non-stop campaign stint in as many weeks with a promise that he would bring change by taking on special interest groups in Washington.

Mr McCain, who beat George W Bush in the New Hampshire primary back in 2000, in turn said he would "bring about change" as he pledged "to do the hard things" if elected.

He made seven campaign stops on Monday, in a state where he has held more than 100 town hall meetings and has revived a campaign which stumbled badly in the summer.

Doubts

Rival Mr Huckabee, whose win in Iowa has been attributed largely to his appeal to a Christian evangelical base, has rejigged his message to focus on a more populist line in New Hampshire.

He appeared with celebrity sidekick Chuck Norris in the state capital, Concord, to sample a lunchtime "Huckaburger", having attracted big crowds to a pancake breakfast earlier.

Mike Huckabee is hoping to capitalise on his Iowa success

Former New York Mayor Rudy Giuliani, whose campaign strategy involves focusing on later primaries in large states like Florida, also made a swing through New Hampshire.

While considered strong on national issues, his support for abortion rights and his three marriages still trouble many social conservatives.

Among them is Christine McKinley, from Nashua, who said she was attracted to both Mr Giuliani and Mr Romney because of their business backgrounds - but had some doubts.

"Some time between now and tomorrow I will be making a decision," she said.

"One thing that concerns me is that there is not as strong a background of family ideals for Giuliani. I have no concerns that Mitt Romney would embarrass us in the White House."

'Retail politics

The candidates, who also include Democrats Bill Richardson and Dennis Kucinich and Republican Ron Paul, will continue to make last-minute appeals as voters go to the polls.

People in the tiny hamlet of Dixville Notch have already decided

Meanwhile, their campaign teams and volunteers will be focused on a get-out-the-vote operation that is the culmination of months of door-knocking, phone calls and hard graft.

They will be all too aware that the undecided voters may change their minds about who to support even as they enter the polling booths.

After all, in New Hampshire, where "retail politics" - as the candidates' face-to-face connection with the voters is known - is all important, loyalties can swiftly change.

Three weeks ago, 32-year-old Chris Gagnon from Manchester thought he would back Mr Obama - but having been impressed when he heard Mr Edwards speak, he volunteered for his campaign instead.

"This is a pretty historic time and this is when New Hampshire gets to shine," he said, explaining his and others' willingness to give up their free time.

"We are at the centre of the world for a little bit - it's unique for a small state. A lot of people in New Hampshire are proud and we would never want to lose this first primary."

Whether the state lives up to its reputation of picking the eventual winners of the party nominations - and the election - remains to be seen. But there's no doubting its commitment to the process of democracy.